Dissecting black spot resistance in polyploid hybrid roses

Authors: Zurn, Jason; ZLESAK, DAVID - University Of Wisconsin; BRADEEN, JAMES - University Of Minnesota; HOKANSON, STAN - University Of Minnesota; Bassil, Nahla

Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2017
Publication Date: 7/29/2018
Citation: Zurn, J.D., Zlesak, D.C., Bradeen, J., Hokanson, S.C., Bassil, N.V. 2018. Dissecting black spot resistance in polyploid hybrid roses. Abstract for International Congress of Plant Pathology: Plant Health in a Global Economy; 2018 July 29-August 3; Boston, MA

Interpretive Summary: Rose black spot is one of the most devastating diseases of cultivated roses for both the home and commercial market. The use of genetic resistance is the most economic and environmentally friendly management strategy for controlling the disease. Currently, little is known about resistance found in roses and only three resistance genes have been characterized. The variety Brite Eyes has been found to be resistant to all but one strain of the pathogen which causes black spot. To better characterize the resistance in Brite Eyes a family was developed by crossing it with the susceptible variety Morden Blush. Results of disease screening of this family indicates that the resistance is controlled by a single resistance gene. Subsequent genetic mapping identified a single resistance gene. The previously mapped resistance genes do not map to this location and do not provide resistance to many of the pathogen strains the Brite Eyes gene does. Therefore the resistance gene in Brite Eyes is a new gene. Disease responses and genetic mapping are also under investigation in another family generated from a cross between two black spot resistant parents High Voltage and Lemon Fizz. These two varieties are resistant for different strains of black spot.

Technical Abstract: Devastating foliar diseases, such as black spot caused by Diplocarpon rosae, pose constant threats to the ornamental quality of outdoor grown roses. Black spot is primarily managed though the use of fungicides, however, there is a high demand for resistant roses which require low chemical inputs. To better characterize resistance in four popular polyploid rose cultivars (Brite EyesTM, High VoltageTM, Lemon FizzTM, and Morden Blush), phenotyping was conducted with 12 D. rosae races. Additionally, two populations (‘Morden Blush’ × Brite EyesTM and High VoltageTM × Lemon FizzTM) were developed to study the segregation of resistance and to map it with the rose Axiom array. ‘Morden Blush’ was susceptible to all races while the remaining three cultivars displayed differing disease responses. A 1:1 segregation ratio was observed for the two populations where each individual was either resistant or susceptible to all races tested to date, suggesting resistance is conferred by a single resistance gene in Brite EyesTM and Lemon FizzTM. High VoltageTM is expected to have a different resistance gene than Brite EyesTM and Lemon FizzTM based on observed disease responses. Linkage mapping in the ‘Morden Blush’ × Brite EyesTM population identified a single resistance gene on chromosome 5 and is different from the three previously described genes. Future work will focus on developing tools for marker assisted breeding and incorporating the broad resistances into new cultivars.